CHAPTER XVIII 

 THE MEASUREMENT OF STANDING TREES 



187. The Problem of Measuring Standing Timber for Volume. 



Standing trees are measured to determine their contents in cubic feet 

 or in terms of manufactured products such as board feet or cross-ties. 

 Trees are measured as a means of determining the contents of entire 

 stands. These may be either average or sample trees, of which only 

 a few are measured, or all of the trees in a stand or part of a stand may 

 be tallied. 



Thevolumescontained in standing trees cannot be measured directly. 

 Even the volume of the logs in the felled tree is computed from the 

 measurement of their diameters and lengths. These computations, 

 tabulated as log rules and as volume tables reduce the problem of esti- 

 mating the volume of standing trees to that of measuring their merchant- 

 able lengths and diameters. 



The cruiser must determine the height of trees either by instruments 

 based on geometric principles of similar triangles, at considerable 

 expenditure of time or by the eye, which is the only practical method 

 where all or a large portion of the stand is to be so measured. 



Still more difficult is the actual measurement of diameters at the 

 top of each log in the standing tree, which must be known when log 

 rules are substituted for volume tables in timber estimating. Instead, 

 the cruiser measures the diameter within reach, that at B.H. or stump, 

 and judges the rate of taper as well as height, by eye, thus arriving at 

 these upper diameters by calculation from a known measurement. 



Diameter breast high (D.B.H) is the only actual and accurate 

 measurement which it is practicable to take upon all or a large per cent 

 of the timber. All upper points are either measured on a few trees 

 only, to obtain averages, or else are judged solely by eye; and since 

 such ocular measurements are confined to dimensions, heights or log 

 lengths, and diameters at upper points on the bole, the cruiser is depend- 

 ent entirely on the computed volumes for these dimensions shown in 

 log rules or volume tables. He may by experience correlate these 

 volumes with their respective dimensions, just as stock buyers learn 

 to guess the weights of animals, and may arrive directly at the volume 



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